UV emitters are formed using multiple quantum wells combined with electrical contacts to the wells. Such contacts are formed of AlGaN in some UV emitters. The wells emit light when a voltage is applied across the contacts. Difficulties in conventional approaches to UV emitter fabrication for short wavelengths are predominantly based on poor electrical conductivity in high Al mole fraction AlGaN, and high resistance contacts to these materials.
The mole fraction of Al determines the bandgap energy (and wavelength of emission) of AlGaN. High Al mole fractions produce a large bandgap—GaN is 3.4 eV (364 nm) and AlN is 6.2 eV (200 nm). The LED or laser requires higher bandgap materials to surround the emitting materials to avoid self-absorption of light, and for the laser, to provide lower refractive index clad layers. Thus, to get shorter wavelength light, higher Al mole fractions are required, and even higher Al mole fractions need to be electrically conducting for the surrounding clad layers.